What will happen to torque if back emf and speed of the DC motor is doubled?(a) Remain unchanged(b) Reduce to one-fourth value(c) Increase four folds(d) Be doubledI have been asked this question in an international level competition.My question is based upon DC Motor Basics -2 topic in section DC Motors of DC Machines

What will happen to torque if back emf and speed of the DC motor is do

1.	What will happen to torque if back emf and speed of the DC motor is doubled?(a) Remain unchanged(b) Reduce to one-fourth value(c) Increase four folds(d) Be doubledI have been asked this question in an international level competition.My question is based upon DC Motor Basics -2 topic in section DC Motors of DC Machines
Answer» The correct answer is (a) REMAIN unchanged Easy explanation: Torque DEPENDS on armature current, so as long as armature current remains constant torque will not change. Speed depends DIRECTLY with back EMF thus, it will definitely become double when back emf is doubled.

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